This invention relates to a system for the inspection of optical components. The optical components to be inspected may include ocular optical components such as contact lenses, eyeglasses, intraocular lenses and the like.
A principal objective of this invention is to provide a system for inspecting contact lenses. Prior to the present invention, optical components such as contact lenses were often inspected manually with the use of a projection-type device such as an optical comparator. Manual inspection systems requiring human intervention are not practical for high-speed production because they are too slow, because human inspectors are prone to making biased judgments, and because inspection results among different inspectors are not uniform.
A principal obstacle to automatic inspection has been the inability to produce high contrast images of optical components, such as contact lenses, so that features such as cuts, edges, scratches, tears and chips could be readily detected and measured. In particular, it has been difficult to obtain high contrast images of entire optical components. As used here, the term xe2x80x9cfeaturesxe2x80x9d includes both beneficial features such as certain topographical characteristics of toric lenses and lens boundaries, as well as detrimental features such as scratches, tears and chips.
The principal difficulty in obtaining high contrast images of optical components such as contact lenses and eyeglasses is that they are transparent. Moreover, in the case of certain optical components, such as hydrated contact lenses called xe2x80x9chydrogelsxe2x80x9d which must remain immersed in a fluid such as a saline solution, the production of high contrast images involves a further complication. That is, the refractive indices for the optical component and the liquid solution may be so similar that boundaries between the two are nearly invisible. Images of the optical component are therefore of low contrast.
Another difficulty in examining hydrogels is that they cannot be kept in a fixed position during examination and will move distances greater than the size of a small feature. Therefore, it is important to obtain a high contrast image of an entire hydrogel so that an image can be captured by an imaging system in a fraction of a second.
Another problem sought to be overcome by the present invention concerns the problem of holding an optical component in position for inspection without human intervention. Indeed, in an automated system it may be critical to have a positioning device that is actually part of the optical system used to illuminate the optical component during the automated inspection.
The novel inspection system of the present invention is predicated upon the surprising discovery that despite the transparent nature of optical components, high contrast images of features of an optical component are produced by focussing light through the optical component. Specifically, the inspection system of the present invention comprises:
(A) image sensing means, having a detector, for sensing an image of an optical component; and
(B) means for focussing light through the optical component prior to reaching the detector of the image sensing means.
Means for focusing light is used to provide xe2x80x9cfocused lightxe2x80x9d. xe2x80x9cFocused lightxe2x80x9d refers to light where the direction of rays is such that an image is formed in their path. Focused light is distinguished from unfocused light in that a given point on or in the optical component under test along the path of the rays of focused light is intersected by substantially a single geometric ray so that there is substantially a one-to-one mapping of rays intersecting the optical component under test to the image sensed by the image sensing means.
Preferably, focused light is transmitted through the optical component being tested such that the light reaches its focus substantially at the entrance pupil of the image sensing means. It is also preferred that the light substantially fills the entrance pupil of the image sensing means, and, preferably, the light does not substantially overfill the entrance pupil. It is also preferred that the light completely illuminates the optical component under test prior to substantially filling the entrance pupil.
In a preferred embodiment, means for focussing light can comprise a collimated light source, comprising an illuminator (any light source) and a collimated holes structure.
In another embodiment, means for focussing light can comprise a refractive collimated light source comprising an illuminator (any light source) and a collimating lens. The means for transmitting focused light can also comprise a reflective collimated light source comprising an illuminator (any light source) and an optical mirror.
In a further embodiment, means for focussing light can comprise a refractive convergent light source comprising an illuminator (any light source) and a converging lens or a reflective convergent light source comprising an illuminator (any light source) and an optical mirror.
Additionally, means for focussing light can comprise a refractive divergent light source comprising an illuminator (any light source) and a diverging lens or a reflective divergent light source comprising an illuminator (any light source) and an optical mirror.
The present invention also provides a novel receptacle or xe2x80x9ccuvettexe2x80x9d for holding and locating an optical component in position during inspection. The cuvette of the present invention comprises a bottom portion having a concave curved inner surface for utilizing the force of gravity to hold an optical component in place. When used in the inspection system of the present invention, the cuvette""s bottom portion is made of a transparent material.
The present invention also provides novel processes for producing a high contrast image of features of an optical component comprising means for focussing light through the optical component to be inspected and then onto an image sensing means to form a high contrast image of features of the optical component on the image sensing means. In a preferred embodiment, the focused light is collimated light.
The present invention also provides novel processes for inspecting an optical component comprising means for focussing light through the optical component to be inspected prior to light""s reaching the detector of an image sensing means to form a high contrast image on the image sensing means.
A detailed description of the present invention is set forth below. However, the embodiments described herein are merely illustrative; further embodiments will be apparent to those having ordinary skill in the art.